The invention concerns a sliding block breech mechanism for a cannon with a breech ring arranged at the rear end of a cannon barrel and with a sliding breech block that slides perpendicular to the longitudinal axis of the cannon barrel in a cavity of the breech ring.
A sliding block breech mechanism of this type is described, for example, in U.S. Ser. No. 898,840 and DE 198 23 785 A1. In this regard, the opposite side surfaces of the sliding breech block (as viewed in the direction of the longitudinal axis of the cannon barrel have several successive lugs of buttress form, which engage corresponding roots of the walls of the breech ring cavity, so that when the cannon is fired, the flanks of the lugs of the sliding breech block that face away from the cannon barrel and that are formed as contact surfaces (known as pressure flanks) are supported on corresponding pressure flanks of the roots of the walls of the breech ring cavity. The pressure flanks of the individual lugs of the sliding breech block and the pressure flanks of the corresponding roots of the walls of the breech ring in these previously known sliding block breech mechanism basically all have the same direction of inclination.
In addition, U.S. Pat. No. 5,014,592 discloses a sliding block breech mechanism whose sliding breech block has three lugs of a modified buttress form, which are arranged in such a way with respect to the corresponding pressure flanks of the roots of the walls of the breech ring that when the cannon is fired, the contact surfaces (pressure flanks) of the two opposing rear-end lugs of the sliding breech block rest on the corresponding contact surfaces of the breech ring, and the contact surfaces of the other lugs press against the corresponding contact surfaces of the breech ring only when the pressure increases. To this end, the contact surfaces of the lugs that are arranged side by side have different flank angles, which, however, are the same as the flank angles of the corresponding contact surfaces of the roots of the breech ring. In this sliding breech block as well, the individual lugs basically all have the same, namely, positive, direction of inclination (when viewed along the longitudinal axis of the cannon tube towards the muzzle of the cannon barrel.
Furthermore, U.S. Pat. No. 5,014,592 discloses a sliding breech block, on which a tie bar is mounted, which can be slid into the breech ring at the rear end. The tie bar joins the two walls of the breech ring and prevents expansion when the cannon is fired.